1. Field of the Invention
The present invention relates to a system and method of controlling one or more ankles of a walking robot, which autonomously achieves conformity and maintains balance within the upper body of the robot when one or more soles of the feet of the robot step on a support surface at an unknown angle.
2. Description of the Related Art
The control of balance is indispensable to biped robots due to their mechanical components and operation. In particular, the control of an actuation unit that actuates the soles of the feet of the robot that step on a support surface is important to the overall balance of the entire mechanism. That is, the soles of the feet must be supported and, at the same time, the balance of the upper body must be maintained. Conventionally, a two depth of field (D.O.F.) control algorithms related to an ankle joint controller has been suggested in a printed publication in Japan in the form of a thesis (see “On Modal Interaction, Reliability and Nonlinear Dynamics of a Model Two D.O.F. Mechanical System Performing Snap-Through Motion,” Nonlinear dynamics Volume 16, Number 3, 239-257, ISSN 0924-090X). However, the control algorithm used in the above thesis does not have a desirable configuration or performance for most robotic manufactures based upon experimental results conducted by the inventors of the present application.
More specifically, the conventional technology uses a control method that calculates a target torque for an ankle of a robot, performs control using this target torque as an input torque, checks the imbalance of the robot using separate dynamics, and then performs a compensation function. However, in the conventional technology, both an error factor attributable to the difference between the sole of a foot of a robot and a support surface and an error factor attributable to the difference between control input and actual behavior are not taken into consideration. Therefore, there is a need for a control system and method which takes these factors into consideration to achieve conformity and better maintain balance within the upper body of the robot.
The description of the related art is intended merely to promote the understanding of the background of the present invention, nor is it intended to acknowledge conventional technology that is well known to those having ordinary knowledge in the technical field to which the present invention pertains.